The invention concerns a device to lift magnetizable carrier particles. Furthermore, the invention concerns a method to lift carrier particles.
In electrographic printers or copiers, two-component toner systems are frequently used that comprise a mixture of ferromagnetic carrier particles and toner particles. A magnetic roller arrangement transports the two-component mixture in a region with little separation between the magnetic roller arrangement and the surface of an applicator element to be inked with toner particles, for example a roller or a ribbon. The toner particles are transferred to the surface of the applicator element, whereby magnetic forces hold back the ferromagnetic carrier particles. However, in practice it can occur that ferromagnetic carrier particles that adhere to the toner particles are transferred with them or are mechanically flung onto the surface of the applicator element. These very hard magnetizable carrier particles are then active outside of the development process and can damage the print system or copier system or, due to the contamination, can cause print image interference.
A method and a device to clean carrier elements in printers or copiers using magnetic fields is specified from DE 101 52 892, incorporated herein by reference. In this patent application, the development process is specified in detail with the aid of two-component systems and the application of magnetic fields to ferromagnetic carrier particles. The content of this patent application is hereby incorporated in the disclosure contents of the present patent application.
It is known from operational practice to use an angle stripper that exhibits a magnetic field to lift magnetizable carrier particles. The angle stripper faces at the distance of an air gap a carrier surface that carries the mixture of toner particles and carrier particles. With the aid of the magnetic forces, magnetizable carrier particles are captured. The problem hereby exists that toner taken along by the carrier particles or freely straying (vagrant) toner dust deposits on the surface of the angle stripper via adhesion or triboelectric or electrostatic charging. Viewed over a longer operation time, toner layers can assemble increasingly stronger, such that it can lead to function disruption. Furthermore, the lifted carrier particles must again be removed from the surface of the angle stripper and, if possible, are again supplied to the two-component mixture in the developer station so that the ratio of carrier particles and toner particles remains constant in the two-component mixture in the developer station. In the developer station, frequently a very limited space is present, such that the return of the carrier particles and also the lifted toner particles causes problems.